Drivers who hit the road in winter with studded tires may be ruining more than just the pavement beneath their cars. They also could be harming their hearts and lungs.

Microscopic road debris kicked up as the tires' spiky metal posts meet the asphalt could pose risks to health, not only for drivers, but also for the people living near highways, Swedish scientists suggest.

Researchers collected airborne particles generated as studded tires rolled over a road simulator at about 40 miles an hour, according to a study published in the latest issue of the journal Chemical Research in Toxicology. They then added this dust to a dish containing human white blood cells, similar to the ones that line the lungs.

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Researchers found that important chemical markers changed after being exposed to road debris — higher levels of three proteins known to increase inflammation and lower amounts of seven proteins that can protect against it. Inflammation is thought to be a cause of heart disease.

"This research is a really helpful reminder to consumers that although we're often focused on the dangers of motor-vehicle exhaust, there's also the friction of tires on the highway to consider," says Doug Brugge, a professor of public health and community medicine at Tufts University School of Medicine in Boston. "These particles can also have inflammatory and toxic effects."

Some states in the U.S., including Illinois and Minnesota, have banned studded tires because they can wear out roads and gut surfaces. Other places allow vehicles to use them only during cold-weather months.

The tires remain popular in Nordic locations, such as Sweden, where the study was done, and in Norway and Finland, where motorists believe they give a better grip, improve traction, and make them feel safer on icy or snow-covered roads. Each tire may contain anywhere from 60 to 120 small studs stuck into the rubber treads.

While most drivers keep their car windows closed in the winter, road particles still can creep in through the vents and heating ducts. They also can filter into the surrounding air and seep into nearby homes.

Brugge, who is currently directing a five-year research project examining the effect of freeway exposure on community health, cautions that observing these effects in a petri dish is a long way from measuring actual effects on human subjects. (All tires release some particles into the air; studded ones just release more of them.)

"You can't just draw conclusions from a cellular study," explains Brugge, who wasn't involved in the Swedish study. These findings also need to be studied in lab animals and in people.

In addition, he points out that the biggest risk of air pollution is cardiovascular disease.

"Inflammation doesn't just affect your risk of asthma or respiratory disease, it happens throughout the body, including the arteries to the heart and elsewhere," he said.